1. Field
The disclosed embodiments relate to the aeronautical field. The subject of the disclosed embodiments is an aircraft nacelle. More precisely, the subject of the disclosed embodiments is a thrust reverser for forming a reverse flow from a secondary thrust flow in the nacelle. The disclosed embodiments also relate to an aircraft fitted with at least one such nacelle.
2. Summary
In general, a nacelle comprises a cowling in which an engine is housed. Air is drawn into the nacelle at a front end of said nacelle, located forward of the aircraft. The nacelle discharges the absorbed air, at high velocity, toward the rear of the aircraft. To allow the aircraft to be propelled, it is necessary for the mass of air passing through the nacelle to have a higher exit velocity than the entry velocity. The exit velocity of the mass of air is increased in a known manner within the actual nacelle.
The air passing through the nacelle is made up of two different flows. A first flow, called primary flow, passes through the engine. The primary flow is ejected directly to the nacelle from the rear of the engine. A second flow, called secondary flow, passes through an air flow channel, before being ejected out of the nacelle. The air flow channel is provided between an internal wall of the nacelle cowling and an external wall of the engine and extends along said engine.
Upon landing, the aircraft applies mechanical brakes for mechanically braking said aircraft. However, once the aircraft is on the ground, it is known to use, in addition to mechanical brakes, thrust reversers. The thrust reversers in particular shorten the landing distance of the aircraft. The term “landing distance” of the aircraft is understood to mean the distance traveled by the aircraft between the moment the landing gear of the aircraft touches the runway and the moment when the aircraft is completely at rest on the runway. The thrust reversers deflect all or some of the air flows leaving at the rear of the nacelle so as to eject them toward the front of the aircraft. The thrust reversers thus create an aerodynamic drag and therefore a braking force called “counter-thrust” force, which contributes to slowing down the aircraft.
As thrust reversers, pivoting-door thrust reversers are known. A nacelle fitted with such a system has doors provided in a thickness of the cowling of the nacelle in a central region of said nacelle. The doors are distributed over a circumference of the nacelle. Such thrust reversers with two doors, each door following a semi-circumference of the cowling, and those having four doors, each door then following one quarter of the circumference of the cowling, are known. In the inactive position, the doors are closed, that is to say they extend over a prolongation of the cowling. In the active position, the doors are open and the pivot axis of the doors is away from the ends of said doors. The deflection of the doors is such that a front part of the doors then extends toward the outside of the nacelle, in a direction approximately perpendicular to a longitudinal axis of said nacelle, and a rear part is housed in the nacelle, so as to at least partly close off the air flow channel. The outflow of air is then blocked and the flow of air is discharged out of the nacelle via the orifices exposed by opening the doors. The front part of the doors, is understood out of the nacelle, enables the flow to be directed toward the front of the nacelle. Such a thrust reverser makes it possible to reverse the thrust arising from only the secondary flow, the openings being made upstream of the primary flow.
One drawback of such a thrust reverser is that it is difficult to maintain an aerodynamic profile on the internal face and on the external face of the cowling at the position of the doors of the reverser. This is because the internal face of the cowling includes means for opening and closing the doors of the reverser, and possibly locking means. In addition, seals are provided along the doors so as to prevent any leakage of air from the nacelle cowling when the doors are closed. All of these devices tend to disturb the flow of air in the cowling.
A thrust reverser having doors for deflecting both the primary air flow and the secondary air flow is also known. The doors of such a thrust reverser are provided on a nozzle of the engine, at the rear end of the engine. When the doors are closed, they extend along the prolongation of the engine and do not disturb either the primary air flow or the secondary air flow. When the doors are open, they close off not only the flow channel for the secondary air flow but also the outlet for the primary air flow in the engine. There also exists a thrust reverser whose doors are provided on the engine nozzle so as to deflect only one of the two flows.
The pivoting doors of the thrust reversers, and in particular those provided on nozzles may deform due to the large distortions to which they are subjected. This is because the air flows through the nacelle under pressure. Moreover, the cowling wall or the nozzle wall is weakened in the region where the doors of the thrust reverser are provided. In addition, the doors of the thrust reversers have a large deformation area, since each door of the reverser represents one half or one quarter of the circumference of the cowling or of the nozzle.
The disclosed embodiments claim to provide a novel thrust reverser with doors for deflecting the secondary thrust flow, which makes it possible to solve the problems relating to the aerodynamic profile of the nacelle and the problems due to deformation of the doors of the thrust reversers such as those currently existing in the prior art.
To do this, the doors of the thrust reverser according to the disclosed embodiments are produced at the rear end of the cowling, forming the trailing edge of said cowling. The term “trailing edge” is understood to mean in general the rear part of an aerodynamic profile. Thus, the number of internal interfaces needed between the doors and the cowling is reduced, especially as regards the seals, since these are necessary only on the front part of the doors. The term “front part” of the doors is understood to mean that part of the doors located upstream of the pivot axis of said doors relative to the flow direction of the thrust flow. The doors are arranged as two circular arcs placed on either side of the circular flow channel for the thrust flow so as to follow substantially an external perimeter of the channel. The doors of the thrust reverser forming the trailing edge of the cowling are closely juxtaposed so that, in the closed position, there is no gap between two doors placed side by side. The expression “placed side by side” is understood to mean that two adjacent doors are juxtaposed, one beside the other, over the entire length of said doors. Advantageously, the thrust reverser according to the disclosed embodiments have a large number of doors uniformly distributed over the perimeter of the cowling, each door having a small area. Thus, the number of doors is no longer two or four, but instead six, eight, ten, twelve or even sixteen or more arranged in a ring on the external periphery of the flow channel for the thrust flow. By reducing the area of each door, the risk of said doors deforming is reduced. When the doors are in the closed position, they extend along the prolongation of the cowling, forming an actual part of said cowling. When the doors are in the open position, they swing out so that a rear part of said doors is housed in the circular flow channel for the secondary thrust flow, so as to block the thrust flow and to expel a reverse secondary air flow out of the nacelle. The term “rear part” of the doors is understood to mean that part located downstream of the pivot axis of the doors. In a preferred embodiment, the doors are connected to the fixed structure of the cowling via fixed beams extending along the prolongation of the cowling. The beams are distributed over the entire perimeter of the cowling. Thus, there is a fixed beam between each pair of adjacent doors, each of these two doors being fastened to said beam. The beams extend for example between an internal wall and an external wall of the cowling, over the entire length of said cowling, including the trailing edge. Since the fixed beams are located between the internal wall and the external wall of the cowling, and along the prolongation of said cowling, they do not impede flow of air. The doors are mounted so as to rotate on the fixed beams. More precisely, each door is mounted so as to rotate on two beams, so as to be able to pivot about a rotation axis passing through these two beams. Advantageously, the doors cover the beams when they are in the closed position.
The disclosed embodiments also relate to a control system for the synchronized opening and closing of a plurality of doors, especially the doors of a thrust reverser. This control system includes actuation means that can be attached to fixed beams extending longitudinally along the prolongation of the doors, a beam being placed between two adjacent doors. Thus, each actuation means may open and close two adjacent doors mounted so as to rotate on either side of one and the same beam. Two adjacent doors actuated by the same actuation means cannot be opened independently of each other. A central door may be boarded by two different doors, each extending along an opposed side of the central door. This central door, flanked by two doors, may therefore be actuated by two different actuation means, each actuating two doors. Thus, the control system ensures that all of the doors are opened and closed smoothly in synchronism. In the case of a thrust reverser, since the actuation means are mounted on the fixed beams there is absolutely no obstruction to the flow of air in the air flow channel.
The subject of the disclosed embodiments are therefore an aircraft nacelle comprising a cowling, an engine housed in an internal volume of the cowling, an annular flow channel for a secondary thrust flow, provided between the engine and the cowling, and at least one thrust reverser for forming a reverse flow from the secondary thrust flow circulating in the annular channel, characterized in that the thrust reverser comprises a plurality of doors provided in a rear part of the cowling, so as to form a trailing edge of said cowling.
According to particular embodiments, the nacelle may have some or all of the following additional features:
the nacelle includes static link rods linking the doors to the cowling, the doors being mounted so as to rotate on the static link rods;
at least one link rod links two adjacent doors;
the link rods are covered by the doors in the closed position;
the thrust reverser includes actuation means for actuating the doors, at least one actuation means actuating two adjacent doors and at least one door being actuated by two actuation means;
at least one actuation means is mounted on a link rod;
at least one actuation means comprises a double-acting cylinder having two actuating rods, one end of each rod being fastened to a door;
the thrust reverser includes rotary means capable of rotating about the axis of the engine, actuation means being mounted on the rotary means so as to actuate the doors on rotation of the rotary means;
the doors are provided with an acoustic coating;
the thrust reverser comprises eight doors;
the thrust reverser comprises sixteen doors; and
the doors are identical to one another and are interchangeable.
The disclosed embodiments also relate to an aircraft comprising at least one nacelle according to the disclosed embodiments.
The disclosed embodiments will be more clearly understood on reading the following description and on examining the figures that accompany it. These are given by way of indication and imply no limitation of the disclosed embodiments. The figures show: